MrsD's comment motivates me to post an older abstract from the following study:

"Complex regional pain syndrome (reflex sympathetic dystrophy and causalgia): management with the calcium channel blocker nifedipine and/or the alpha-sympathetic blocker phenoxybenzamine in 59 patients," Muizelaar JP, Kleyer M, Hertogs IA, DeLange DC, Clin Neurol Neurosurg. 1997 Feb;99(1):26-30.

Department of Neurosurgery, University of California, Davis, Sacramento 95817, USA.

Complex Regional Pain Syndrome (CRPS) is the new name for entities formerly known mostly as Reflex Sympathetic Dystrophy and Causalgia. Treatment of CRPS with either the calcium channel blocker nifedipine or the alpha-sympathetic blocker phenoxybenzamine was assessed in 59 patients, 12 with early stages of CRPS, 47 with chronic stage CRPS. In the early stage CRPS patients, 3 of 5 were cured with nifedipine and 8 of 9 (2 of whom had earlier received nifedipine) with phenoxybenzamine, for a cure rate of 92% (11 out of 12). In the chronic stage CRPS patients, 10 of 30 were cured with nifedipine; phenoxybenzamine cured 7 of 17 patients when administered as a first choice and another 2 of 7 patients who received nifedipine earlier, for a total late stage success rate of 40% (19 out of 47). The most common side effects necessitating discontinuing the drug were headaches for nifedipine and orthostatic dizziness, nausea and diarrhoea for phenoxybenzamine. All male patients on phenoxybenzamine experienced impotence, but this did not lead to discontinuing this agent and immediately disappeared after stopping the drug. These results once again stress the importance of early recognition of CRPS, and treatment with either of these drugs could be considered as a first choice for early CRPS, especially because in this series this treatment was not combined with physical therapy making it very cost-effective. In the chronic stage of CRPS, treatment with these drugs was much less successful (40%), even though it was always combined with physical therapy, but it can still be considered, either as a first choice or when other types of treatment have failed. [Emphasis added.]

PMID: 9107464 [PubMed - indexed for MEDLINE]

http://www.ncbi.nlm.nih.gov/sites/entrez

What's inclear from the abstract alone is how long a patient with chronic CRPS must remain on the drug(s) once a successful result has been established. But even a 40% success rate looks pretty good, all things consider: assuming you can avoid the contraindications of the two drugs. Wonder what happened to the treatment? I'll try to pull the article.

Mike


PS Okay. Here we go. The problem was that iv phenoxybenzamine was pulled by the FDA a while back, and that's was was being used in at least one of these studies. See, "Intravenous Regional Phenoxybenzamine in the Treatment of Reflex Sympathetic Dystrophy," Malik, Vinod K, et al, Anesthesiology March 1998 - Volume 88 - Issue 3 - pp 823-827, html full text at http://journals.lww.com/anesthesiolo...he.36.aspx#P24 Nevertheless, an oral tablet is on the market, marketed under the name of Dibenzyline.

Last year, some promising results with the oral tablet were reported in chronic CRPS patients using the drug on a long term basis. "Treatment of complex regional pain syndrome type I with oral phenoxybenzamine: rationale and case reports," Inchiosa MA Jr, Kizelshteyn G.Pain Pract. 2008 Mar-Apr;8(2):125-32. Epub 2008 Jan 7 full text at http://www.rsds.org/2/library/articl...izelshteyn.pdf

Department of Pharmacology, New York Medical College, Valhalla, New York 10595, USA. mario_inchiosa@nymc.edu

The nonselective alpha-adrenergic antagonist, phenoxybenzamine, has been used in the treatment of neuropathic pain syndromes, specifically, complex regional pain syndrome (CRPS) types I and II. This agent has also previously been used in intravenous regional peripheral blocks for treatment of CRPS I; however, an intravenous preparation of phenoxybenzamine is not currently available in the U.S.A. In this case series, systemic administration was more appropriate for three of the four patients, as their syndromes had spread beyond the initial area of surgery or trauma. We report an apparent clinical benefit in three of the four patients following oral administration. We postulate that this may be due to the noncompetitive (irreversible) blockade of alpha(1)- and alpha(2)-adrenergic receptors. We further hypothesize that this blockade could reduce stimulation of an increased population of adrenergic receptors in hyperalgesic skin, blunt the stimulation by norepinephrine of alpha(2)-adrenergic receptors on macrophages, and ultimately reduce the release of proinflammatory cytokines from cellular elements.

PMID: 18194348 [PubMed - indexed for MEDLINE]

http://www.ncbi.nlm.nih.gov/pubmed/1...ubmed_RVDocSum

BUT, in April, 2008, the FDA required that a product warning be placed on the (physician's) product information sheet, which reads in part as follows:

PRECAUTIONS

Carcinogenesis and Mutagenesis

Case reports of carcinoma in humans after long-term treatment with phenoxybenzamine have been reported. Hence long-term use of phenoxybenzamine is not recommended. Carefully weigh the benefits and risks before prescribing this drug... [Emphasis added.]

http://www.fda.gov/Safety/MedWatch/S.../ucm117801.htm Unfortunately, I can't seem to pull a complete copy either a full copy of the new warning language or the prescribing information sheet (which is odd) and in fact that new warning doesn't even appear in the patient friendly Medline Plus page for phenoxybenzamine, last revised September 1, 2008, http://www.nlm.nih.gov/medlineplus/d...s/a682059.html but the foregoing warning language from an official FDA site is enough for me, when it comes to considering the long-term use of the drug. No thank you.

So the question is, can the use of nifedipine, combined with the short-term use of oral phenoxybenzamine, be effective in the treatment of CRPS? And for that one, the jury may still be out.